The effects of medications on oral cocaine self-administration will be investigated. Specifically, chronic administration of d-amphetamine, modafinil, and atomoxetine will be studied. Six rhesus monkeys will serve as subjects. The oral route will be used for several reasons. Cocaine is abused orally, and importantly intake of cocaine via the oral route is similar to intake of cocaine via the intranasal route. Most studies of drug effects on cocaine self-administration have used the i.v. route;however, it is important to determine if findings obtained with the i.v. route can be extended to other routes. Four studies will be conducted. In all studies treatment drugs will be administered chronically. The first and second studies will use FR and PR schedules, for these have been the most commonly used schedules in i.v. cocaine experiments. One measure of drug effects will be the ratio of responses under the PR schedule to the ratio of responses under the FR schedule. In these two studies drug effects will also be examined on the resumption and extinction of drug reinforced behavior as well as on the maintenance of behavior. The third study will employ a design that separates "drug seeking" and "drug consumption." Thus, in the initial component (an Interlock schedule FR 480, FI30 min schedule), medication effects on behavior can be assessed in the absence of cocaine in the body. The fourth study concerns the selectivity of medication effects. Cocaine and an equally reinforcing saccharin solution will be concurrently available under non independent Variable-Ratio schedules. These schedules generate patterns of responding that result in the concurrent intake of both reinforcers within the same time segments. Importantly the schedules permit variations in the distribution of responding allocated to each reinforcer without necessarily decreasing the total number of reinforcers obtained. The results of the proposed studies will examine the generality of earlier findings with humans and monkeys that d-amphetamine decreases cocaine intake, and the studies will determine the feasibility of using agonist type medications that are currently approved for use in humans.